(b) Group-specific blood should be given. If time permits, test the
patient in the transfusion facility without relying on previous records. Evidence of the
patient's blood group must not be taken from cards, dog tags, drivers' licenses, or other
such records.
(2) Begin the routine compatibility testing procedure. If the clinician cannot
wait the length of time required for a complete crossmatch, release the blood and
continue the crossmatch after release.
(3) Complete the compatibility testing. If incompatibility is detected at any
stage of the testing, immediately notify the patient's physician and the blood bank
physician.
1-52. CROSSMATCH IN PRESENCE OF PROLONGED CLOTTING TIME
Blood samples from patients with coagulation abnormalities may not be fully
clotted when serum and cells are separated. When such serum is incubated with donor
RBCs, a fibrin web may trap masses of RBCs making it difficult to determine whether
true agglutination has occurred. Coagulation of such blood specimens (except those
deficient in fibrinogen) can usually be accelerated by the addition of thrombin to the
patient's serum. One drop of thrombin (50 units/mI) per milliliter of serum, or the
amount of dry thrombin that will adhere to the tip of an applicator stick, will convert the
remaining fibrinogen instantly. Keep in mind that the addition of excess thrombin may
cause nonspecific agglutination of all donor cells tested. If this occurs, additional serum
must be obtained and glass beads may be added to help clot-formation. This should
circumvent the nonspecific agglutination problem. If anticoagulated specimens are
used, the donor cell suspension must be well washed to be certain that there is no
carry-over of fibrinogen. It may be necessary to add one drop of protamine; however,
protamine sulfate may cause rouleaux and, in excess, may also prolong clotting.
1-53. COMPATIBILITY TESTING AFTER INFUSION OF SYNTHETIC PLASMA
EXPANDERS
Plasma expanders, such as some dextrans or other large molecular weight
plasma substitutes, may cause rouleaux, and difficulty with compatibility tests. When
fresh serum that was collected before the infusion is not available, the saline
replacement technique should be performed. The saline-antiglobulin test will usually be
compatible; the high protein test may appear incompatible.
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